Lecture Notes on the Use of Logic Works (Version 4)

Revision 2.0.1 - February 15, 2000

by: Jason S. Thweatt

0. INTRODUCTIONThese notes are meant as a supplement for students taking ECpE 2504 (Introduction to Computer Engineering) orECpE 3504 (Digital Design I), especially for those who lack experience in the use of Logic Works. Logic Worksprovides the student with a great deal of flexibility in the design and simulation of the digital circuits that he or shewill implement using the chip set and trainer kit. Since the design and simulation steps are meant to verify thecorrect operation of a circuit before it is implemented, and as a result, save valuable time, every student who isenrolled in one of the classes listed above should have a firm foundation in the use of this software. Although theinformation contained herein is being pitched to two different levels of students, students in both classes should geta lot out of most of the material. In general, however, references which are made for the use of individual orprimitive gates are aimed more at 2504 students, while references made to 7400 devices are aimed at 3504students.

If you have any questions about any topic that is, or is not, covered herein, or you believe that somethingmentioned may be in error, please contact me with your questions or concerns. My current e-mail address isjthweatt@vt.edu.

Note: Unless mentioned, all mouse-click are left clicks. "Double-click" and "click-and-hold" should be performedas indicated.

1. TOOLS

1.1 Drawing WindowThe Drawing Window, also called the Design Window, will contain the circuits you design, and is your maininterface with the software. Circuits in the Drawing Window act in concert with timing information in theTiming Window, as will be seen later.

1.2 Parts PaletteThe Parts Palette, or the Library, contains all of the parts that you will use to design circuits, and some partsthat you will not use. What you use will depend on the course you are taking, and your own ingenuity indesigning circuits.

1.3 Timing WindowWhen active, the Timing Window will display the waveforms associated with your circuit. This is the otherwindow where important things happen.

1.4 Drawing ToolbarThe Drawing Toolbar is used to control the Cursor and modify the status of the Drawing Window. Theoptions of the Drawing Toolbar can turn the Cursor into a magnifying glass, a logic probe, a precision deletiontool, a labeling tool, and a wiring tool. It can also be used to cut, copy, paste, and obtain information aboutselected parts.

1.5 Simulation ToolbarThe Simulation Toolbar is used to control the Timing Window. The Simulator can be used to control therate at which simulations are generated, or to step through simulations in incremental time steps. TheSimulator options can be accessed through the Simulation menu of the Command Toolbar.

2. BASIC DESIGN

2.1 Part PlacementTo place a part in the Design Window, double-click on the desired part name in the library. A shadowedversion of the part will appear at the cursor. Place the part at the desired location and click.

The part selected will remain active for placement until it is deactivated. If you want to select a new part,double-click on that part name and repeat the previous steps. If you just want to deactivate the part withoutselecting a new one, press the space bar or the Escape key.

Users of Logic Works 3 may recall that the Palette contained an Orientation Tool. This function has beenmoved to the Schematic menu of the Command Toolbar. When the Orientation command is selected, the usermay select from among the eight part orientations offered on the graphic menu. Once an orientation isselected, all parts inserted into the diagram will appear having that orientation.

2.2 WiringTo make connections between logic devices, click and hold at the end of a input or output pin of one of thedevices, or at an existing node of the wire network. A node is created in a network at any point where a wirebranches to form multiple connections. Move the cursor to the point where you want the wire to end. Thiscan be another pin, another wire, or an empty location. Be careful, because this method of wiring can produceundesired nodes at points where wires cross.

Another method of wiring involves the use of the wiring drawing tool on the Drawing Toolbar.

2.3 EditingTo move a part or a wire, click on it and drag it to the desired location. Selected parts will appear highlightedin black, and wires will appear highlighted in yellow. Be careful when moving parts, because wires attachedto moving parts will “stretch,” and unwanted nodes may be created.

To move a large number of parts, click and hold the mouse button at an empty location and drag the mouseuntil all of the parts you wish to move are contained (at least in part) in the window that has been created.When you release the mouse, all parts that can be moved will appear highlighted. Click and hold the mouseon any of the highlighted parts, and they will all move together. Again, be careful, because wires may crosswhen you move parts.

To delete a part or wire, click on it and press the delete key. To delete a large number of parts, select them allas before (click and hold, then drag) and press the delete key.

If you get in trouble, the Undo command in the Edit menu has a very good memory.

3. THE DRAWING TOOLBARAs mentioned earlier, The Drawing Toolbar is used primarily to change the function of the cursor. It allows youto change attributes such as part placement and wire type, make corrections in circuits, insert text, change the viewof the design window, and perform logic probes of your circuit.

The Drawing Toolbar is most easily thought of as having five parts: File Management, Part Movement andModification, Cursor Modification, Drawing Window Modification, and Part Type.

3.1 File ManagementThe first four buttons of the Drawing Toolbar are used for file management. Starting from the left, these fourbuttons are used to Create new files, Open an existing document, Save the active document, and Print theactive document. Each of these commands, as well as the remainder of the file management commands, canbe found in the File menu of the Command Toolbar.

3.2 Part ModificationThe next five buttons of the Drawing Toolbar are used for part movement and modification. Continuingfrom the Print button, these buttons are used to Cut parts which have been selected on the Drawing Window,Copy selected parts to the Clipboard, Insert the contents of the Clipboard into the Drawing Window,Duplicate the selected parts and make them available for placement using the cursor, and Get and SetInformation about the selected part. In the case of the last command, only one part can be selected at a time.

3.3 Cursor ModificationThe next seven buttons of the Drawing Toolbar are used for Cursor Modification. These functions areprobably the most useful of those on the Drawing Toolbar. You will find some more useful than others, buteach one will be covered in greater detail here.

3.3.1 MagnifyThe Magnification cursor will present a centered and magnified view of the location that is clicked.Magnification can also be done using the Magnify command under the View menu.

There is no Reduce cursor, but reduction can be done using the Reduce to Fit command under the Viewmenu, or through various zooming techniques, all of which will be discussed later.

3.3.2 ProbeThe Probe tool has two uses. First, when the cursor is touched to a pin and held (click and hold), thatpin’s logic level is displayed.

Second, if you enter a logic value while probing a pin, the pin will take on that value. Be careful whensetting values, as logic conflicts can occur which are not immediately detectable. You should not use thisfunction unless you are an experienced user of Logic Works, and even then, you will probably not find itthat useful.

3.3.3 PointerThis is the default cursor selection. When enabled, the cursor will function in all of the ways previouslydescribed.

3.3.4 ZapIn several cases, you will want to delete one part of a wire without deleting the whole mesh, or you maywant to delete one object in a particularly tight space. The Zap cursor allows you more flexibility indeleting objects. When enabled, clicking on an object with the zap cursor will delete only the part of anobject that appears at the tip of the cursor. This is very useful for removing errant parts of wires.

3.3.5 TextUsing the Text cursor, you can insert text into schematics, i.e. titles, chip descriptions or wire and pinlabels. Clicking on the text button changes the cursor into a pencil. When the pencil tip is inserted in arandom location, a text window appears at that location, and miscellaneous text can be inserted. Type inthe desired text, and click the text cursor elsewhere once you are finished. To edit text, click the textcursor in the vicinity of existing text.

When the pencil tip points at a pin, wire, or part, you can name that object. When labeling a pin, clickthe pencil tip on the pin, and a window will open. Type the desired text in the window, and click themouse or hit Return. The text will appear in blue above the pin.

When labeling a gate, click the pencil tip on the gate, type the desired name into the window which opens,and click the mouse or hit Return. The name will appear in red above the gate.

When naming a signal, click the pencil on the end of a pin or on the wire which will carry the signal.Type the signal name, and click the mouse or hit Return. The name will appear in red at some pointalong the signal. If the Add Automatically option is selected in the Simulation menu, the signal namewill also appear in the Timing Window.

3.3.6 WiringTwo palette tools are available for wiring: normal wire, which can be placed using the Normal cross, andbus wire, which can be placed using the Bold cross. Bus wire is not used frequently in digitalapplications, but be aware that any wire connected directly to a bus becomes a bus, even if the normal wirecursor is selected.

Unlike wiring done with the normal cursor, wiring done with the wiring cursor does not have to begin at apin.

3.4 Drawing Window ModificationThe next four buttons of the Drawing Toolbar affect what is displayed on the Drawing Window. Continuingfrom the Bus Wire button, the next four buttons cause the design page to Zoom Out, cause the design page toZoom In, Fit the design page to the Drawing Window, and display the parts in the design page at NormalSize.

3.5 Part TypeThe last two buttons control the body of parts that are used in circuit design. The first button opens thePROM / RAM / PLA Wizard. Of the three features of this option, the only option which might be useful to3504 students is the Programmable Logic Array (PLA) construction tool. For more details on the use of thisoption, consult Chapter 10 of the Logic Works 4 manual.

The second button opens and closes the Parts Palette.

4. LIBRARIESIn most circuit design, there are only a few libraries with which you will need to concern yourselves.

4.1 Simulation Gates.CLFThis library contains individual logic gates: AND, OR, NOT, NAND, NOR, XOR, and XNOR. Dependingon the type of gate, different numbers of inputs are available. You will notice that several of the gates haveinverted inputs available, but from the standpoint of determining chip costs and gate delays, it is not a gooddesign practice to use those gates, assuming that you use primitive gates to design circuits in the first place.

4.2 Simulation IO.CLFThese parts represent individual input/output devices. Of the devices which are only found in this library,three sets of devices may be of use to designers.

4.2.1 Seven-Segment DisplaysThere are multiple seven-segment displays in the I/O Library. Of those, the ones called 7-Seg Disp Inv -(Color) operate in the same way as the seven-segment display included in the 2504 kit: when a logic zerois applied to one of its pins, the corresponding segment becomes lit, and when a logic one is applied, thecorresponding segment stays unlit. Be sure to keep this in mind when you perform a design using aseven-segment display. The other seven-segment displays in this library have segments which light onlogic one; these are not the devices you should use.

4.2.2 LEDsThe LEDs in this library can be thought of and used in the same way as the LEDs in your trainer kit. Tocorrectly wire the LEDs, ground the pin which is connected to the bubble, and connect the other pin to theoutput device which you are using to drive the LED. When properly grounded, LEDs will light on logicone.

4.2.3 Pushbuttons and SwitchesIn addition to the Binary Switch (which will be discussed later), the I/O Library contains a Single-PoleDouble-Throw (SPDT) pushbutton, a SPDT switch, and a Single-Pole Single-Throw (SPST) switch. AnSPST switch is one which is either open or closed. A SPDT switch can take on two different logic levels,depending on what connections are made to the switch inputs. A SPDT pushbutton is like a SPDT switch,except it normally takes on one value, and only goes to its other value when momentary contact is made.For double throw switches, make sure that both inputs are connected to circuit elements which can take onknown values.

4.3 Simulation Logic.CLFThe parts in this library are individual higher-level logic devices, such as adders and registers. Students in2504 and 3504 may find these devices useful:

4.3.1 AdderThe Logic Library contains a number of adders. To simulate the adder included in the 2504 chip set, youshould select the part called Adder-4. This adder has the same input, output, and carry pins as yourAdder chip.

4.3.2 Flip-FlopsThe individual D flip-flops operate in the same manner as the D flip-flops in your chip set. The D inputis the same in Logic Works as it is on your chip. The C input represents the clock pin. The Q and Q'outputs represent the standard and complemented outputs. The S and R lines represent the set and reset(clear) lines of the flip-flop. Note that these pins are active-low, as represented by the bubbles on theirinputs. If you know that you will never have to preset the flip-flop, connect the S input high. Toimplement a clear function into a sequential circuit, connect the R input to a binary switch (See 4.5.2:Binary Switches.) whose value is high (logic 1) for the time in which you do not want the circuit to bereset.

The pins on the JK flip-flop follow the same conventions as the D flip-flop.

4.3.3 MultiplexersThis library contains a number of multiplexers. To simulate the multiplexer included in the 2504 chip set,your best bet is to use two of the Mux-4 devices. The names of the pins on this device are much the sameas those on your multiplexer chip.

4.4 7400DEVS.CLFThese parts represent devices in the 7400 series of integrated circuits, and correspond to the chips that youpurchased. For reasons of convenience, most of the design that you do in ECpE 3504 will be simulated inLogic Works using 7400 devices instead of chips.

• The 7400 devices have pin numbers that correspond to the actual integrated circuits. While the pinlocations do not match exactly, a well-laid out design that uses 7400 devices can save time when the timecomes to wire a circuit.

• Having the 7400 devices laid out saves time when preparing Whole Chip Costs and Fractional ChipCounts for reports.

4.5 DEMOLIB.CLF This library contains miscellaneous parts, of which five in particular are very useful.

4.5.1 +5V, Ground Just as you should never keep a input pin floating when wiring a chip, it is a good design practice to wireinput pins high or low if you know that they will always have a certain logic value. These two signals canbe used to provide constant logic levels of 0 or 1 to the various pins of your circuit. In Logic Works, 7400devices do not have power or ground pins, but there are times when you will want to keep reset pins,enable pins, clear pins, or input pins at logic 1 or logic 0. 4.5.2 Binary Switches The 2504 and 3504 kits contain banks of DIP switches, which can place a logic 1 or logic 0 on a givenpin. In Logic Works, Binary Switches work the same way. A Binary switch is a special kind of SPDTswitch whose inputs are already connected to logic 1 and logic 0. The designer has only to wire the outputof the switch to an input pin or named signal, and toggle the value by clicking on the switch. If the switchdoes not toggle, make sure that the simulation is active by pressing the Reset and Run buttons on theSimulation Toolbar. Binary switches (and SPDT pushbuttons) make good manual clocks; they work the same way as the push-button switches in your lab kits. 4.5.3 Binary Probes When debugging a physical circuit, it is a good practice to use a wire and an LED to observe the logiclevels within the circuit. Connect one end of the wire to the LED, and use the other end to probe theoutput. Binary probes work the same way in Logic Works. They are better than the Probe on thePalette in that once they are placed, they remain in the circuit, and are updated whenever the circuitchanges.

Multiple probes can be places at different locations in a circuit, allowing you to troubleshoot manylocations at once.

The values displayed on the probes follow the rules of Boolean algebra, but conditions may exist such thatthe probe displays a non-numeric condition.• (X) Don’t know/Don’t care condition: An output is at an unknown state.• (Z) High impedance/No input condition: The probe is not connected to an input.• (C) Conflict condition: An output is being forced to conflicting logic levels.

In general, these conditions are not desirable, and you should check your circuit for errors should oneoccur.

4.5.4 Clocks Although it may seem strange, the clock in this library will not be very useful when you need a clock inyour circuit. In the case where you are changing the inputs of a circuit using binary switches, a clockoscillates much too rapidly to be of any use. In cases like these, you will want to model the clock in muchthe same way that it exists in your trainer kit: as a push-button switch. (i.e., another binary switch or aSPDT pushbutton) In the case where you are using a Timing File to drive the inputs, it can be verydifficult to synchronize the start of the clock with the start of the timing file. In these cases, the best thingto do is to drive the clock from the timing file as if it were another input. (See 5.2.2: AutomaticSimulation for more information on the details of Timing Files.)

The best use for clocks that I have found is in generation of timing files for use in combinational logiccircuits. Suppose that you have a circuit whose inputs are one of n Boolean variables. If you wish tocompare the output of your circuit with the information contained on a truth table, you would need towrite a timing file that contains 2n lines of information. If your circuit contains more than 4 inputvariables, the creation of such a timing file can become tedious and prone to error. To generate such a timing file, you can build an n-bit binary counter, which requires n clocks. Place theseclocks in the Design window, and give each one a name corresponding to the variables of your circuit.This is important, as timing files only work when the names of the signals contained in the file correspondexactly to the names of the signals in a circuit. To make the counter work, each variable (or clock) must have a frequency that is half that of the variablewhich immediately precedes it. For example, the clocks have default high and low times of 10nanoseconds. You can let that be the high and low time of the clock that represents your least significantbit. Now, each clock after the first must have high and low times which are double that of the clockbefore it. Remember: to halve the frequency, double the period. To change the timing parameters of thesecond clock, select it by clicking on it. Then choose the Simulation Parameters option under theSimulate menu bar. A window will appear allowing you to modify the clock parameters. Give the secondclock high and low times of 20 nanoseconds. Then, as stated earlier, repeat this for each clock,progressively doubling the high and low times for each clock. Once you have done this for all of the clocks, you can use the Single Step button on the SimulationToolbar to step through a full count cycle (all zeros to all ones). If you named your clocks correctly, thisinformation will appear in the timing window. Follow the directions given below for exporting timingfiles (See 5.3 Importing and Exporting Timing Files.) Now, when you need a timing file that tests all ofthe inputs of a combinational circuit, assign names to the inputs of the circuit that match the signal namesin the timing file. Then, follow the directions below for importing a timing file. Use the timing file youcreated to drive the circuit, and you will end up with a timing file showing the correct inputs and outputs.

5. SIMULATION AND TIMING

5.1 The Simulation Toolbar The Simulation Toolbar is your interface with the Simulator and the Timing Window. Its features give youcontrol of the speed and status of the simulation, the status of the various signals of the circuit, and the size ofthe Timing Window. The Simulation Toolbar is best thought of as having three parts: Signal Status, WindowStatus, and Simulator Status

5.1.1 Signal Status The first seven buttons control the status of signals, and to a degree, their appearance in the TimingWindow. Starting on the left, these buttons function as follows:

5.1.1.1 Toggle The first button Toggles the presence and absence of the Timing Window. 5.1.1.2 Add Signals The second button Adds Selected Signals to the Timing window if the Add Automatically option ofthe Simulation menu is not already selected. 5.1.1.3 Triggers This button opens the trigger option menu. It will not be of great use to 2504 or 3504 students.

5.1.1.4 Simulation Parameters This button can be used to carry out the same functions as those which can be performed using theSimulation Parameters command under the Simulation menu. 5.1.1.5 Stick Signals This button can be used to Stick Signals at a given logic level. A stuck signal is one which remainsat one logic level despite changes which might be affecting. 3504 students will study stuck-at faults,but students will not find this option generally useful. 5.1.1.6 Reset Simulator This button Resets the Simulator. The Timing Window is cleared of all waveforms, and regardless ofthe current time indicated in the Simulation Time Window, the next time step taken will be time zero. 5.1.1.7 Clear Unknowns This button tries to clear all signals which have unknown values. Sometimes this is not possible, as apart may have undriven inputs, which by definition provide Z inputs to the part.

5.1.2 Timing Window Control The next three buttons control the scale of the Timing Window. These buttons Zoom In on the timingscale (the Timing Window contains less time), Zoom Out on the timing scale (the Timing Windowcontains more time), and set the timing scale to its Normal (Default) Size. 5.1.3 Simulator Speed The Simulator Speed control consists of three buttons, a slidebar, and a counter. Starting on the left,these controls have the following functions:

5.1.3.1 Single Step As mentioned previously, the Single Step button can be used to a single step in the simulation of acircuit. A step is defined as the shortest amount of time which is required to observe a change in thesimulation. As a result, a step can be of any size, and usually reflects the time length of the quickest-changing variable, or of the shortest delay path. 5.1.3.2 Stop Simulator When the simulator is running, the Stop Simulator button stops the progress of the simulation. Itdoes NOT reset the simulation; while stopped, the simulation can be resumed by pressing the Runbutton or by selecting a Simulation Speed on the slidebar. While stopped, the simulation can also beadvanced in single steps. 5.1.3.3 Simulation Speed The sliding toolbar can be used to Change the Speed of simulation. This is most visibly reflected inthe speed of the waveforms in the Timing Window. The simulation speed can be changed duringsimulation, or it can be set while the Simulator is stopped. When the indicator is slid all the way tothe left, the Simulator is stopped. 5.1.3.4 Run Simulator Pressing the Run button causes the Simulator to run at its highest speed. This is true whether or notthe Simulator is already running. 5.1.3.5 Simulation Counter This window shows the Current Time Step, i.e., the amount of simulation time which has passedsince the last reset. The time shown in this window reflects the time shown in the timing window,and the simulator speed selected on the sliding toolbar.

5.2 The Timing Window When active, the Timing Window will display all changes in all named signals. Events that cause signals tochange include toggling binary switches, clock pulses, and timing file inputs. These types of changes can becharacterized as static (manual) or dynamic (automatic).

5.2.1 Manual Simulation Switches and probes can be used in the manner described above to achieve a degree of manual simulation.Since Logic Works is an event-driven simulator, a change in any input signal causes all named signals tobe updated. As a result, a change in any of the signal values, say, through the toggling of a switch, willcause all of the observable values to change. These changes manifest themselves primarily in two ways.Either all of the binary probes in our circuit will be updated, or the waveforms in your timing window willbe updated. 5.2.2 Automatic Simulation Having to toggle a large number of binary switches in a complex circuit can become tedious, lead to error,or just end up taking a lot of time, especially if you lose your place and have to start over. Fortunately,Logic Works is equipped with the means to automate the simulation process, through the use of timingfiles. A timing file is a compact method of telling the Simulator what signal you want to apply to a giveninput at a given point in time. A typical timing file requires at least three headers and at least one row of data, with one element of eachrow corresponding to each header. Those headers are: • $T: This header gives the current point in time. Time in Logic Works is generally measured from T

= 0, and each time step can be thought of as one nanosecond• $D: This header gives the delay or difference between the time step of the current row and that of the

next row. While this information is redundant given the information provided by the first header(and can therefore be left out), you will see this in any timing file which is generated by Logic Works.

• $I: This header denotes each signal that is being driven by the timing file, and should be immediatelyfollowed by the name of the signal. When timing files are exported, all signals, input and output,will be denoted by the header $I, followed by the signal name

Keeping in mind what each header means, we can see that each row of data corresponds to a point of time($T), where each signal will have a given value ($I) for a given amount of time ($D).

5.3 Importing and Exporting Timing FilesOnce you have created a timing file in an application such as Notepad, you will want to use it drive the inputsof your circuit. To do this, you must import the timing file into the Simulator. Select the Simulation menu ofthe Command Toolbar, and select the option called Import Timing. Select the name of your timing file, and abroken-line version of the inputs will appear in the timing window.

When you press the Run button on the Simulation Toolbar, Logic Works will cycle through these inputs,applying them at the correct locations. Any outputs that are named in the circuit and appear in the Timingwindow will also be updated, and their waveforms generated.

Again, in order for a timing file to be successfully imported, all of the signals named in the timing file mustcorrespond to signals that are named in the circuit diagram. Also, the data contained in each row must allcorrespond to a given header. It is a good idea to place one tab stop between each header, and one tab stopbetween each piece of data in a row. Since most tab stops default to eight characters, and the header $I takesup three of those characters (including the space), it is a good idea to keep the names of your signals to threecharacters or less. A signal name should be long enough to distinguish it from others, but not so long that thetabs and spaces turn your timing file into a jumble of letters and numbers.

Once you have obtained a set of correct outputs, you may be asked to provide these outputs in a tabular ortextual form, you can do this by exporting the timing file. Select the Simulation menu of the CommandToolbar, and select the option called Export Timing. Give the file a name, and the information contained inthe Timing window will be saved in a format similar to timing files that you write yourself.

5.4 DelaysUnless modeled otherwise, devices in Logic Works are treated as nearly ideal devices, having a propagationdelay of one nanosecond between the input and the output. Such is not the case in real life; according to mostdatasheets, a typical device such as a 7400 chip, or a dual-input NAND gate, has a worst-case delay of 22nanoseconds between a change in the input and the corresponding output. There are times when you will beasked to model this delay in your simulations, in order to meet certain timing or frequency criteria.Fortunately, Logic Works gives you a way to do this.

To change the delay in one or more gates, hold down the Control key, and click on all of the devices forwhich you want to change the delay. Then, under the Simulation menu, select the Simulation Parametersoption. A window will appear, showing the current shortest and longest delays for the selected gate or gates.For all parts, this defaults to one nanosecond. To change the delay, simply type in the delay that you want theselected gate or gates to have. The delay that you type in will be applied to all gates which you select in theDesign window, so be sure that all of the gates which you select have the same time delay.

To change the delay in a chip (i.e., a 7400 device), you must first unlock the subcircuit containing the gates.Right-click on the device and select Device Info. A window containing various information on the selecteddevice will appear. The dialog box labeled Lock Opening Subcircuit should be checked. Click on the box toremove the check. Now, you can edit the parameters of the gates inside the chip as if they were individualgates. To do this, double click on the chip you wish to edit. A Design Window containing a gate and pinlayout of the IC will appear. As before, select the gates whose timing parameters you wish to edit, and followthe instructions for changing the gate delay.

To save time when changing the chip delays in a large circuit, lay out the entire circuit by placing all of thechips that your circuit requires into the Design Window. You need not wire the circuit in order to implementthe propagation delays. For each type of chip in the circuit, select one and perform the procedure for changingthe delays of the gates on that chip. When you do this, all of the chips of that type which are already in thedesign window will have the same delay. Note that this procedure will not work for gates taken from theSimulation Gates.CLF library. Instead, you will have to follow the procedure given for changing the delay inmultiple primitive logic gates.